Disclosed herein is an aqueous ink composition that is suitable for both direct and indirect printing applications. The aqueous ink composition comprises water; a co-solvent; an encapsulated resinous pigment; a polymer latex; and a low molecular weight humectant solute; wherein the total solids content of the aqueous ink is from about 2 to about 25 percent by weight based on the total weight of the aqueous ink composition.
In direct printing machines, a marking material is applied directly to a final substrate to form the image on that substrate. Other types of printing machines use an indirect or offset printing technique. In indirect printing, the marking material is first applied onto an intermediate transfer member, and is subsequently transferred to a final substrate. A two step printing process can comprise applying an ink in an imagewise fashion onto an intermediate receiving member such as a drum, belt, etc., using an ink jet print head. The ink wets and spreads on the intermediate receiving member to form a transient image. The ink forming the transient image can then undergo a change in properties such as partial or complete drying, thermal or photo-curing, gelating, etc., and the resulting transient image can be transferred to a final image receiving substrate.
U.S. patent application Ser. No. 14/066,716, which is hereby incorporated by reference herein in its entirety, describes a printing process and an aqueous ink for indirect printing applications comprising water; a co-solvent; a colorant; and a polymer latex comprising an aqueous dispersion of polymer particles wherein the polymer latex has a softening temperature of from about 60° C. to less than 105° C. and a glass transition temperature of from about 45° C. to about 100 C. The inks are particularly formulated for printing on an intermediate transfer member where they are fully dried before transfer.
While known ink compositions and processes are suitable for their intended purposes, a need remains for improved ink compositions with certain characteristics. A need remains for inks, specifically for an ink set that has a high solid loading but with significant improvement in stability, jetting performance, and print quality, suitable for both direct to paper with and without paper pre-treatment, and indirect printing where the intermediate substrate is treated and/or coated with a sacrificial release layer.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.